This is the solution for Sony Ericssom Xperia X1 with a Display Not Rotate in Landscape and portrait mode when sliding the keyboard or keypad.
This solution below may help on how to fix if this kind of problem occurred. But before applying or use this solution, you may first try to play a tricks on your Xperia X1 by putting it near into a large magnet or speaker. If the display respond it means that there is something wrong with the flex ribbon cable. I have tried this tricks and effective for quick troubleshooting.
SE Xperia X1 Display Rotate problem Solution
Once the display won't respond or rotates, you may then refer to the solution above and do a replacement on highlighted components. You may then locate the sensor chip, its mounted near camera switch and try to replace the said chip.